In general, one of methods for obtaining 3D image information combines 2D image information obtained from various views. In so doing, it is quite important to find corresponding points of the same physical location and the same characteristics in a plurality of images including the same object or scene.
Particularly, for images obtained using a plurality of cameras, a technique for compensating for color difference which rises from different color values of the obtained images is required. To compensate for the color difference, a conventional method uses Macbeth color checker chart.
For the color compensation, Korean Patent Publication No. 10-2010-0035497 discloses a method for compensating for the color by obtaining an image with the Macbeth color chart in each camera, calculating the color of each color patch with pixel average, and calculating a unit conversion matrix which equals the color of the patches. However, this method has the following problems.
Firstly, the color compensation method using the Macbeth color chart considers only hardware characteristics of the camera and thus needs to compensate for the color frequently because it cannot reflect other conditions (for example, lighting and weather change) in the actual shooting. Secondly, the method is inapplicable when parameters of the camera automatically change. Thirdly, since the Macbeth color chart image is uniform, it is difficult to automatically match the corresponding point. Fourthly, since even the camera of the same model has its own nonlinear camera response function per parameter of the camera, the color is not precisely compensated merely using the conversion matrix.
Meanwhile, for the color compensation as stated above, it is necessary to find the accurate correspondence between pixels of the same color in a plurality of images. Yet, the conventional method uses motionless image or geometrical registration to find the correspondence of the images and thus has the following problems.
Firstly, when the scene (the image) includes one or more planes, the accurate correspondence between the pixels is not attained using the geometric registration. Secondly, when the camera is close to the scene, the geometric registration is not properly obtained. Thirdly, since the accurate pixel correspondence is not obtained, the color comparison is not precise and the image similarity reliability calculated with the sum degrades.
Hence, what is needed is a method for addressing the problems of the color compensation methods using the Macbeth color chart and for enhancing the similarity reliability of the corresponding image for the color compensation of the corresponding image.